1. Field of the Invention
The present invention relates generally to a telescoping mast assembly useful in sundry applications and, more specifically, to a telescoping mast assembly suitable for mobile field use.
2. The Prior Art
Telescoping masts are well known safety devices useful in law enforcement, industrial, military or commercial applications. Such masts are portable devices which can be readily deployed when needed and readily returned to a storage position when not in use. Typical applications are those in which equipment or devices require elevation in order to optimally accomplish their intended function. It may be desirable, or essential, to elevate floodlights, cameras, antennas, or other surveillance equipment by means of a telescopic mast assembly in order for such devices to function optimally. By way of example, one common application is to mount a telescopic light mast upon the roof of a vehicle for illuminating a wide area surrounding the vehicle. The mast must quickly and reliably deploy when necessary, and retract against the roof of the vehicle when not in use. Law enforcement officials, in particular, have found such devices useful in the field.
Heretofore, telescoping masts have been either pneumatically, hydraulically, or chain driven. Pneumatic drive motors require airtight seals between telescopic mast sections in order to function as intended. However, the environment in which such masts are used makes maintaining an airtight condition between mast sections problematic. Contaminants, or radial ice, deposited between mast sections, or at the junction will stop the mast from descending or cause damage to the mast sections, and can easily destroy the seal required for efficient operation of the pneumatic drive. In the event that the pneumatic integrity of the seal is destroyed, the mast will fall gravity with a potential for disastrous consequences.
A further disadvantage to pneumatically powered telescoping masts is that they can only assume one of two positions. Either the masts are fully extended or fully retracted. In many applications, however, because of obstructions or other considerations, it is desirable to have the telescoping mast sections in a partial state of extension or retraction. A further disadvantage with pneumatic drives is that they are relatively heavy in weight, limiting their suitability for vehicle roof applications. In addition, such drives are expensive to manufacture, assemble, and maintain, which limits their commercial appeal.
Finally, in applications where the unit is used on uneven terrain, pneumatic units cannot work consistently on grades exceeding fifteen degrees and, if the loading at the top is high, even less. The tubes on pneumatic masts on slopes exceeding the limit may bend at the joint, causing air leakage at the junction and a corresponding failure. A unit accordingly is needed which can safely maintain structural integrity on slopes exceeding fifteen degrees.
Hydraulic systems for elevating masts suffer from many of the same shortcomings. Hydraulic drives are relatively heavy in weight and are expensive to manufacture, assemble, and maintain. Moreover, such drives are vulnerable to damage from contact with the environment since hydraulic lines are exposed. Additionally, contaminants can infiltrate the hydraulic system and cause malfunction or failure.
Chain driven telescopic masts likewise suffer from the same deficiencies. The drive mechanisms are relatively heavy in weight and are expensive to manufacture, assemble, and maintain. The chain link mechanism is also exposed and susceptible to damage from contact with environmental objects.
Other shortcomings common to the aforementioned conventional telescopic mast drives and devices are that the wiring to the outboard end of the mast is exposed and can be damaged by inadvertent contact with surrounding obstacles or suffer from damage from exposure to the elements. Moreover, the masts are generally fabricated from conductive material from the base to the top end. An electrical charge introduced into such, masts from inadvertent contact with exposed overhead electrical lines will, accordingly, be transferred to the vehicle below, causing a potential for danger to the operators on the ground. Available systems lack effective means for preventing such a charge transfer, such as a fuse system. However, even were fuses implemented into wiring of available units, because the wiring is exposed to the elements, such fuses would be prone to damage and deterioration from exposure to the elements and may not function as intended when they are needed.
The present invention overcomes the aforementioned deficiencies in available telescoping mast systems by providing a ball actuator drive system. A telescoping extendible mast section is housed within a base mast section which mounts to a base plate. A first ball actuator mounts to the base plate and drives the base mast section between a horizontal storage position and a vertical work position. The base plate ball actuator comprises an electrically powered motor which drives a ball screw along a stroke path. A remote end of the ball screw is attached to a bottom end of the base mast section and pivots the base mast into alternative angles of elevation by pushing and pulling against the bottom end of the base mast section. The base mast section can, accordingly, be placed and held in any angle required between the storage and work positions.
The telescoping extendible mast section is likewise driven between an extended position and a retracted position by a second ball actuator drive system. The second drive system is fixedly mounted within the base mast section and comprises a drive screw affixed at a remote end to the extendible mast section. Movement of the drive screw along a stroke path pushes and pulls the extendible mast section into alternative positions between the extended and retracted positions. The extendible mast section can, as with the base mast section, be placed and maintained in any of the alternative positions to conform to the physical constraints of the space in which the mast is used. The extension of the extendible mast section is independent of the elevational operation of the base mast section, affording the user a wide range of options for optimally positioning the telescoping mast. Positive actuation of the mast sections in both directions by the drive motors will operate effectively on slopes of twenty degrees or more.
Additional stages of telescoping mast sections may be employed in order to increase the maximum reach of the mast. A ball drive actuator for each such additional section can be likewise utilized. The mast sections and ball drive actuators are relatively light weight and are readily assembled and maintained. In addition, the wiring which supplies power and control signals to the ball drive actuators and to electrical devices mounted to a remote end of the mast assembly is housed entirely within the axial passageway of the coaxial mast sections. Protected from exposure to the elements, or damage from contact with surrounding objects, degradation or damage to the wiring is avoided.
The top section of the mast is composed of non-electrically conductive material in a preferred embodiment. Such a composition prevents that section from transferring an electrical charge to the vehicle to which the mast assembly is mounted. Danger to operators below from inadvertent contact between the remote section of the mast and exposed overhead conductors is, thereby, avoided. Further, inasmuch as the wiring to the top of the mast is protected within the mast sections from the elements and from damaging contact with environmental obstructions, an effective and reliable fuse system can be incorporated into the wiring harness which will stop the transfer of electrical current from the wires into the base of the unit and therefrom into the vehicle frame.
Accordingly, it is an objective of the present invention to provide a telescoping mast assembly having an improved drive system for motivating a plurality of mast sections between storage and work positions, and into alternative positions therebetween.
A further objective of the invention is to provide a telescoping mast system having means for encasing and protecting wiring which is routed from the base to the remote end of the mast.
Yet a further objective is to provide a telescoping mast system having a positive drive mechanism associated with each mast section, which independently pushes and pulls its respective mast section between an up and a down position, and into alternative positions therebetween.
Another objective is to provide a telescoping mast system having improved means for electrically isolating the underlying vehicle on which the mast system is mounted.
Still a further objective is to provide a telescoping mast system which is relatively lightweight and protected from deterioration due to exposure to the elements.
A further objective is to provide a telescoping mast system comprised of relatively inexpensive components which are economically and readily assembled and easily maintained.